In the past, information has been entered into computing systems through a wide variety devices. Several of the more familiar devices are the keyboard, punchcards, magnetic tape, and the like. Recently, alternative devices such as the light pen, the trackball, and the mouse have gained popularity.
A mouse is generally a device which rests upon a surface and which, when moved over the surface, translates such movement into physical position signals. These signals, when provided to a computer in connection with a visual display, can be utilized to move a cursor, for example, about the visual display. U.S. Pat. Nos. 3,541,541; 3,835,464; 3,892,963; and 3,987,685 are illustrative of mouse apparatus.
A trackball is generally a device which remains stationary when in operation. A trackball generally includes a ball which is supported within a housing and which is permitted to rotate in the housing. The ball usually protrudes through the top of the housing so that the user can supply motive force directly to the ball at the point of protrusion. Trackballs are manufactured by a number of companies including Wico Corporation of Niles, Ill. and Measurement Systems, Inc. of Norwalk, Conn.
The existence of both mouses and trackballs is indicative of the fact that a mouse can perform certain tasks which a trackball cannot, and vice versa. For example, a mouse provides control over the information being input in that the movement of a mouse over a surface is analagous to movement of the hand in a writing situation. With a mouse, the motion of the mouse over a surface can be viewed as an operation in a Cartesian coordinate system. Thus, there is no need to convert the motion of the mouse from another coordinate system into the Cartesian coordinate system typically used on display screens.
Conversely, a trackball permits the coverage of large distances quickly. When the user imparts motive force to the ball, the momentum of the ball causes the ball to rotate through several complete rotations before the ball comes to rest. On the other hand, the motion of the ball can be viewed as an operation in the spherical coordinate system. Thus, the user is required to mentally convert the motion of the ball from the spherical system into the Cartesian coordinate system.
Thus, it can be seen that a device that provides both a trackball and a mouse function would be highly desirable, as well as more hardware efficient. Heretofore, no such device has existed.
While the obvious solution would be to merely turn a mouse or trackball upside down in order to obtain the other function, there are certain mechanical problems associated with such a solution. One such problem would be the requirement of an additional supporting system, since the original device would have been designed to support its rotating member in a downward or upward direction, but not both. Additionally, when the mouse or trackball is turned over and operated, the direction of physical motion of the rotating member will be encoded in a reverse direction from its normal operation.